Electrical switches



July 3, 1962 R. G. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 1 In ya u tars,

RALPH G. AREY DAVID E. CLARKE July 3, 1962 R. G. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 2 NIH] Inven tor5,

RALPH G. AREY DAVID E. CLARKE Atty.

y 1962 R. e. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 3 //0 l, #2;\Jii. I /06 z l0? HES [721/672 tors,

RALPH e. AREY DAVID E. CLARKE July 3, 1962 R. G. AREY ETAL I 3,042,776

ELECTRICAL SWITCHES 6 Sheets-Sheet 4 Filed Sept. 16, 1959 RALPH G. AREYDAVID E. CLARKE July 3, 1962 R. G. AREY ETAL 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 e Sheets-Sheet 5 In 7/672 tors,

RALPH G. AREY DAVID E. CLARKE MQ WJ July 3, 1962 R. G. AREY Em 3,042,776

ELECTRICAL SWITCHES Filed Sept. 16, 1959 6 Sheets-Sheet 6 Inventors,RALPH s. A Y

DAVID E. CL E Att y.

in phantom lines;

3,042,77 6 ELEQTREAL SWITCHES Ralph G. Arey, Brockton, and David E.Clarke, Norton,

Mass, assignors to Texas Instruments Incorporated,

Dallas, Tex., a corporation of Delaware Filed Sept. 16, 1959, Ser. No.840,327

' 17 Claims. (Cl. 200-116) The instant invention relates to electricalswitch structures, and more particularly, to thermally responsive switchstructures.

An object of this invention is to provide an improved switch structureincorporating a new and improved combination of interrelated parts.

A further object is to provide such a switch structure whichaccommodates the use of compressive resilient biasing means for biasingoperating parts thereof.

Another object is to provide such a switch structure utilizing a thermaltype latch means and a new and improved mechanical latch means, whichmechanical latch means functions Withoutupsetting the calibration of thethermally responsive latch means thereof.

A further object is to provide a thermally responsive switch which isalso mechanically actuable repeatedly as an on-olf switch withoutupsetting the calibration of the thermally responsive means thereof.

Another object of the invention is to provide such a switch structurewhich exhibits improved electrical contact pressure characteristics.

Another object of the instant invention is to provide such a switchstructure which affords snap-opening and snap-closing of the electn'calcontacts.

Among the further objects of the instant invention are the provisions ofa switch which is' durable, accurate, reliable in operation, compact,easily calibratable, has vibration stability, which embodies a minimumnumber of parts, and which is simple in construction and economical tomanufacture. I

Other objects will be. in part apparent and in part pointed outhereinafter.

The invention accordingly comprises the elements and combinations ofelements, features of construction, and v arrangements of parts whichwill be exemplified in the structures hereinafter described, and'thescope of the application of which will be indicated in the followingclaims.

in the accompanying drawings, in which one of the various possibleembodiments of the invention is illustrated: v

FIG. 1 is a vertical section, with some'parts broken away and others inelevation, in a thermally responsive switch embodying the instantinvention, showing the 3,042,776 Patented July 3, 1962 ice FIG. 9 is atop plan view of a part of the resetting means of the switch of theinstant invention;

FIG. 10 is a sectional view taken on line 10-10 of FIG. 9; and

FIG. 11 is an elevational view, partly in elevation and partly insection, of a part of the mechanical latching means of the switch of theinstant invention.

Similar reference characters indicate corresponding parts throughout theseveral views of the drawings.

Dimensions of certain of the parts as shown in the drawings have beenmodified for the purposes of clarity of illustration.

The instant invention relates to electrical switches of the class suchas that described and claimed in the earlierfiled copendingapplications, Serial No. 732,550, filed May 2, 1958, now matured intoPatentNo. 2,912,546, issued: November 10, 1959, and Serial No. 837,754,filed September 2, 1959, now matured into Patent number 3,022,402,issued February 20, 1962.

Referring to'FlG. 1, an electrical switch embodying the instantinvention is shown taking the form of a circuit breaker indicatedgenerally by the reference numeral 20. The switch includes a base orcasing 22 which carries a bushing 24 having an annularly extendingflange 26, which mates with a correspondingly-shaped recess 28, providedby a cover member 84 for casing 22 which maybe sea sleeve 38 disposed inanother aperture of smaller di ameter'in button assembly 32, as bestseen in FIG. 1. Stem 36 is secured in fixed relation to button 32 bymeans of a beveled portion 40 on stem 36, which abuts the lower portionof flanged sleeve 38 (as best seen in FIG. 1), and a nut 42 which isthreaded onto the upper end of stem 36, in a suitable recess provided bybutton assembly 32. \After nut 42 is tightened to secure stem 36 tobutton assembly 32, asealing compound 44 is introduced and a covermember 46 is applied to close the opening in buttonassembly 32, all ofwhich is 'clearly'illustrated in FIG. 1.

Bushing 24 provides an abutment or. projection 48, which is received ina vertically extending slot 49 pro vided by button 32. Abutment orprojection 48, which interfits with slot 49, prevents rotation of thepush button relative to the switch casing and also provides one partsthereof in full lines in the retracted, contacts-open position and theparts in dashed lines in the reset, contacts-closed position;

FIG. 2 is a vertical sectiontaken on line 2-2 'of'FlG. l, with someparts shown in full lines and others in section; 1 1

PEG. 3 is a top plan view on an enlarged scale of'the thermallyresponsive member of the switch;

FIG. 4 is a front elcvational view of the thermally responsive membershown in FIG. 3;

FIG. 5 is an end view of the thermally responsive member shown iii-FIGS.3 and 4;

FIG. 6 is a view similar to FIG. 1, showing the parts thereof in fulllines in the reset, contacts-closed position, and showing the partsthereof in dashed lines in the retracted, contacts-open position; i I

FIG. 7 is a sectional view taken on line-7-7 of FIG. 6, with certain ofthe parts shown in full lines-and others means for limiting downwardmovement of the push button 32, as viewed in FIG. 1. Anannulus or bandof a color contrasting with that of-the push button member 32 and thebushing 24 may be provided, if desired, to indicate the relative switchpositions, in a well-known manner. Bushing 24 is externally threaded, asat 50, for the reception of a nut or nuts (not shown) for mounting theswitch on a support.

Stem 36 is provided with a portion 52 of enlarged diameter, having abeveled portion 54 adjacent the smaller diameter portion 36a of stem 36.

and resiliently biases member 58 against beveled portion 54 and awayfrom button 32 in a contacts-closing direc- Manually operable resettingmeans 34 further includes an abutment member tion. The upper end ofspring 60, which is disposed about reduced diameter portion 36a of stem36, abuts a nut 62, which is in threaded engagement with the portion ofthe stem 36a adjacent sleeve 38. Aperture 39 has a cross sectionalconfiguration which is complementary to that of nut 62 and therebyserves to prevent relative rotation between nut 62 and button assembly32. Adjustment of the compressive biasing force of spring 60 may beeffected by rotation of stem 36 relative to nut 62 before nut 42 istightened and the sealing compound 44 and cover 46 are applied. As willbe explained in greater detail below, spring 60 serves as a means forproviding desired contact pressure.

As best seen in FIGS. 1, 9 and 10, aperture 59 provided by abutmentmember 58 has a substantially larger diameter than the outside diameterof smaller diameter portion 36a of stem 36, whereby member 58 has aloose, unconfined fit with this portion of the stem when the resettingmeans is in the reset contacts-closed position, as shown in FIG. 6.Aperture 59 also includes a countersink or beveled portion 55 engageablewith interfitting beveled portion 54- provided by enlarged diameterportion 52 of stem 36 under the bias of spring 60 when the resettingmeans is in the retracted contacts-open position shown in FIG. 1.

Manually operable resetting means 34 includes an annular abutment 61 onmember 58, and is movable from the positions shown in full lines in FIG.1 to the positions shown respectively in full lines in FIG. 6, into en-'gagement with a thermally responsive unit indicated generally as at 100to move the latter from a contacts-open to a contacts-closed position,as will be more fully described below.

Referring now particularly to FIGS. 3-5, the exemplary thermallyresponsive unit illustrated therein comprises a thermally responsiveelement formed of a section of composite material. The high-expansioncomponent of the composite material, as shown in the embodiment of thedrawing, is indicated at 1112 (HES) and the low-expansion component isindicated at 104 (LES). Thermally responsive unit 100 provides alongitudinally extending slot 106 through which enlarged diameterportion 52 of stem 36 extends whereby thermally responsive unit 100 isslidably mounted on stem 36. Thermally responsive unit 100 provides alongitudinally extending bridging portion 108, which carries movablecontacts 110 and 112 which are electrically connected to thelowexpansion side 102 thereof. Thermal unit 100 thus serves as a movablymounted means for carrying movable contacts 110 and 112. Thermallyresponsive unit 100 is further provided with and carries a pair ofopposed spaced slotted arms 114 and 116, as best seen in FIGS. 2 and 5.

Accordingly, thermally responsive unit 100 provides an electricallyconductive path leading from contact 110 through the bridging portion108, through arms 114 and 116, to contact 112. Due to the heating of thethermally responsive element 100 upon the flow of electrical currenttherethrough, the thermally responsive element flexes or warps to thedotted-line condition shown in FIGS. 2, 4, and 7, whereby arms 114 and116 are deflected away from each other. The distal ends'of arms 114 and116 are engageable with abutment 61 provided by member 58, and thesurface presented by this abutment is tangential to the are traced bythe distal ends of arms 114 and 116 as the latter move away from eachother under said warping of the thermally responsive element.

Referring again to FIGS. 1 and 2, thermally responsive member or unit100 is resiliently biased from the contacts'cl'osed position (shown infull lines in FIG. .6 and in dashed lines in FIG. 1) to thecontacts'open position, as shown in full lines in FIG. 1, by means ofacompression spring 64 which is disposed about stem 36. The upper end ofcompression spring 64 abuts a layer of electrical and heat insulatingmaterial 68 provided on the lower surface. of thermal member as clearlyseen in FIGS. 1 and 2. Insulating member 68 serves as an insulatorspring seat and prevents short circuiting of the thermal element byspring 64' and stem 36 and localizes the heat at the thermal element.The other end of compression spring 64 abuts a latching ring member 160,as will be described in greater detail below.

Casing or housing 22 provides a pair of abutments 99 for limiting theextent of upward movement of thermally responsive member 100 from acontacts-closed to a contaets-open position by engagement thereof withthe upper surface of bridging portion 108, as clearly shown in FIGS. 1and 6. Housing member 22 provides recesses 70 for the reception ofterminals 72 and 74, respectively.

Terminals 72 and 74 are so configured as to interfit with casing 22 forrigid mounting. A sealing compound 80 is disposed about terminals 72 and74 when in final assembled condition. Terminals 72 and 74 respectivelycarry fixed contacts 76 and 78 for co-operative engagement respectivelywith movable contacts and 112, as shown. As is clear from the drawing,thermally responsive member 100 provides a bridging member electricallyconnecting contacts 76 and 78 when the thermally responsive member is ina contacts-closed position, as shown in FIG. 6.

It will be noted that thermally responsive member 100 is prevented fromrotation about its axis and with respect to the casing by the engagementof respective surfaces thereof with adjacent portions of the casing.Referring to FIGS. 1 and 2, it will be apparent that the marginal edgespresented by the thermally responsive unit 100 engage adjacent surfacesof the casing to prevent undue lateral shifting thereof as well as toprevent rotation thereof. Further, the slidable mounting of thethermally responsive member 100 on portion 52 of stem 36 also serves toprevent undesired lateral shifting of the thermal element with respectto the casing.

Stem 36 is compressively biased in a contacts-opening direction by meansof a compression spring 120, housed in spring cup 122, which may beformed of a metallic or phenolic material. One end of spring abuts'arivet 124 which serves to mount spring cup 122 in housing 22, and theother end of spring 120 is received in an axially extending recess 126provided by the lower end portion 146 of stem 36, as clearly seen inFIG. 1.

Housing 22 provides a recess formed by walls 132 and 136 for housing thespring cup and mechanical latching means which will be described ingreater detail below. Spring cup 122 is disposed in and is entirelyenclosed in the recess provided by housing 22, as clearly seen in FIGS.1, 2 and 6. Compression spring 120 thus urges stem 36 and abutmentmember 58 (through engagement of beveled portion 54 of the stem andbeveled portion 55 on the abutment member 58) and button 32 in acontacts-opening direction.

Switch 20 includes mechanical latching means for latching the stem in areset, contact-closed position when the thermal element 100 isthermallylatched to the stem for movement therewith as a unit in thecontacts-closing direction. The mechanical latching means operatesindependently of the thermal latching and is mechanically actuablerepeatedly-without upsetting the calibration of the thermally responsivemeans.

Stem 36 is provided intermediate its lower portion 146 and portion 52,with a portion 140 of enlarged diameter. The diameter of portion 140 isconsiderably greater than the diameter of portion 52 of stem 36. Portion140 includes a circumferentially or peripherally extending groove whichprovidesa detent surface 142, as clearly seen in FIG. 1. Adjacent thelower portion of portion 140 is a beveled portion 144, which intersectswith the lowermost portion 1460f stem 36, which portion 146 is ofslightly smaller diameter than that of portion140, for a purpose to bedescribed below. 1 t

Detent surface or circumferentially extending groove 142 is adapted toreceive and mate with a plurality of balls 150 for latching engagementtherewith. Referringnow to FIG. 8, ball means b is shown as exemplarilycomprising three balls, circumferentially spaced about stem 36 andmounted for movement in a direction normal to the longitudinal axis ofstem 36, toward and away from, or into and out of engagement with,detent surface or groove 142, by means of suitable openings 152 providedby spring cup member 122 (as clearly shown in FIGS. 1 and 8). It shouldbe understood that in the practice of the instant invention a greater ordifferent number of balls could be provided, if desired. It has beenfound,however, that the employment of three balls, as illustrated,provides a stable mechanical latching arrangement.

Balls 150 are urged for movement into latching engagement'with detentsurface or groove 14-22 by movable detent means comprising a latchingring 160, which may,- for example, be formed of a hardened stainlesssteel.

Latching ring 16! is slidably mounted on spring cup 122 and is guidedfor reciprocal vertical movement between the housing walls 132 providedby casing 22 and the outside circumferential surface of spring cup 122,and is thus confined to reciprocal sliding movement in a verticaldirection, as seen in FIG. 1, Latching ring 160 includes an angularlydisposed wedging surface 162 which is engageable with balls 15% to urgethe latter into engagement with detent surface 142 upon downwardmovement of latching ring 160, as viewed in FIG. 1'. The outercircumferential portion of latching ring 160 is so shaped as to providea spring seat for the lower end of spring 64 to abut, whereby spring 64also compressively biases latching ring or detent ring 166 for movementdownwardly to'urge balls 150 into latching engagement with detentsurface 142 when thermal element ltltl'is moved into the contacts-closedposition.

Latching ring 16% includes a lower beveled portion 164 which is disposedat an angle to wedge surface 162 and which permits balls 159 to moveoutwardly in opening 152, relative to detent surface 142 and spring cup122 so as to permit disengagement of stem 36 frornthe balls 150 tothereby permit stem 36 tomove outwardly to the retracted, contacts-openposition under the bias of compression spring 120.

The angle of beveled surface 162 on the latching ring 16%) which engagesthe balls 15b is such as to render the eiiective downward thrust of thelatching ring 160 and the spring 64 greater than the upward thrust ofthe stem spring 12%) when the thermal element is in the contactsclosedposition. I

The detent latching ring 169, as shown in elevationin FIG. ll, furtherincludes an upper beveled portion 166 which is adapted to mate with anannularly or circumferentially extending projection 168 provided byspring cup 122 so as to limit upward movement of the detent ring 160.

It should be understood that spring cup 122 and latching ring 169,although shown as circular in cross section, could be of other geometricconfigurations, if desired.

The operation of circuit breaker 20 will now be described. With parts inthe respective positions shown in full lines in FIG. 1, thermallyresponsive element 1% is in the retracted, contacts-open position,member 58 is in the retracted position and biased by spring 60 againstbeveled portion 54 provided by enlarged diameter portion 52 of stem 36,and button assembly 32, which is fixed to stem 36, along with stem 36and member 58, is biased to the retracted position under the bias ofcompression spring 12%, whereby a band formed of a' color contrastingwith that of the push button 32, if provided, would be visibleexteriorly of the casing. It should be noted that in this condition,ball means 150 are disposed outwardly and are loosely in engagement withthe circumferential outer surface of the portion146. of stem 36 (which,as shown, is of lesser diameter than 6 portion 140). Thermal element100, when in the contacts-open position, is maintained against stop 99by spring 64, which is in a relatively unstressed condition a when inthe contacts-open position. Spring 64, when in the relatively unstressedcondition in the contacts-open position, exerts little, if any, biasingforce on latching ring 166).

When push button 32 is depressed to the advanced or resetcontacts-closed position, the parts will take the respective positionsshown in full lines in FIG. 6. As movement of push button 32 from theposition shown in FIG. 1 to that shown in FIG. 6 ensues, the abutment 61provided by member 58 moves intothermal latching engagement with thedistal ends of each of arms 114 and 116 provided by the thermallyresponsive element 166i, whereby the thermal element .100 and thestem 36are thermally latched together as a unit for movement in thecontacts-closing direction. Continued movement of push button 32 resultsin the compression of spring 60, (which by proper pressure setting, willprovide desired contact pressure) compression of spring 64, which iseffective to urge latching ring 160 downwardly, as viewed in FIG. 1, andmove wedge surfaces 162thereof into engagement with balls 150 to urgethe latter to tion, and that of biasing latch ring 160 into wedging er1-gagement with ball means 150 to urge the latter into latching engagementwith stem 36.

With further movement of push button 32 and stem 36 to the resetposition shown in FIG. 6, ball means 150 will traverse the axial orlongitudinal extent of portion 146 of stem 36 and engage beveled portion144 adjacent larger diameter portion 14%, whereby the resistance tobeveled portion 144 and engages the vertical portion 145 movement ofstem 36 to the reset or contacts-closed position will be sharplyincreased, requiring a greater force .to be applied against push button32. With the application of increased force to push button 32 toovercome the resistance to movement of'stem 36 presented by the beveledportion, when ball means 150 traverses the "balls 150, which resistancediminishes suddenly as the balls liititraverse the beveled portion 144and engage the vertical portion 145. At the point Where the balls 154Dleave wedge surface 144 and engage surface 145,

the applied resetting force would be at a maximum and since at thispoint there is little or no resistance to movement of the stem 36 to thecontacts-closing direction, the contacts will be closed with a snapaction. This snap closing, which is advantageously afforded by theinstant invention, is particularly desirable in eliminating or at leastreducing contact erosion, which is generally characteristic ofdeviceswhich do not afi'ord' a quick snap closing of contacts. 7

When push button 32 has been moved downwardly as seen in FIGS. 1 and 6,to the contacts-closed position sufficiently so that engagement ofmovable contacts and 112, respectively, with'fixed contacts 76 and 78has taken aoaawe mechanically latched in the contacts-closed position bythe ball means 150 and detent surface 142 and latch ring 166, under thebias of spring 64. The movable abutment 58, which abuts the thermalelement 100 at the distal ends of arms 114 and 116 to provide thethermal latching, by being movable relative to the stem and being springbiased in a contacts-closing direction, provides contact pressure and agap override to assure desired contact pressure.

With the parts in the contacts-closed, reset position shown in FIG. 6,an electrically conductive path is established leading from terminal 72through contact 76, contact 110, thermally responsive bridging portion166, through each of arms 114 and 116, contact 112, to contact 78 andthrough terminal 74. Upon the flow of current of sufiiciently highvalues along the electrically conductive path just described, thermallyresponsive element 100 is heated by the current passing therethrough andexpands thereby moving arms 114 and 116 outwardly and away from eachother to a dashed-line position as shown in FIGS. 2, and 7.

When'the thermally responsive element 100 warps or flexes suflicientlyto move the distal ends of arms 114 and 116 out of engagement withabutment 61 provided by member 58 to the broken-line position shown inFIGS. 2 and 7, member 58 moves to the broken-line position shown in-FIG. -7 under the bias of spring 60 and thermally responsive unit 100is no longer restrained in the contacts closed position and immediatelybegins to move upwardly to the contacts-open, retracted position, asshown in full lines in FIG. 1, under the resilient bias exerted bycompression spring 64.

Referring now to FIG. 6, as thermally responsive element 100 moves tothe contacts-open position shown in dashed lines in this figure underthe bias of spring 64, said spring 64 expands and sharply decreases thebiasing force exerted against latch ring 160 which is urging balls 150into latching engagement with detent surface 142. As the thermal elementin the unlatched condition continues to move upwardly to thecontacts-open position shown in dashed lines in FIG. 6, the spring 64Will continue to expand to further decrease the downward thrust againstlatch ring 160, to a point at which the effective downward thrust of thelatch ring 160 and spring 64 will become less than the upward thrust ofspring 120. At this point, stem 36 will begin to move upwardly and thelower peripherally extending portions of groove 142 will earn balls 150outwardly against ring 160. Since latching or detent ring 160 isconfined to vertical movement, ring 160 in this condition, will moveupwardly against the now relatively unstressed spring 64 until thebeveled surfaces 164 are adjacent balls 150, which will thereby permitballs 150 to move outwardly out of engagement with latching detentsurface 142, whereby stem 36 will then quickly move to the retracted,contacts-open position under the bias of spring 120. Outward movement ofstem 36 under 'the bias of spring 120 is limited by engagement of member58 with the casing when bevel 54 of stem 36 is engaged with countersinkor beveled portion 55 of member 58, as clearly shown in FIG. 1.

It should also be noted that after balls 150 are in engagement with theouter surface of portion 146, when stem 36 has moved to a retractedposition as shown in FIG. 1, ring 160 may move downwardly to theposition shown in this figure under the force of gravity and the,

in FIG. 1, thermally responsive member 100 will still be heated and dueto the thermal expansion thereof, arms 114 and 116 may be disposed inthe outwardly displaced position shown in dashed lines in FIGS. 2 and'7.Accordingly, upon depression of push button 32 from the retractedposition (shown in dashed lines in FIGS. 6 and 7 and in full lines inFIG. 1), while the thermally responsive element 1% is still in theheated condition with arms 114 and 116 still deflected outwardly (asshown in the dashed line portions of the figures mentioned above),

downward movement of push button 32 and stem 36 fails to bring abutment61 into engagement with the distal ends of arms 1 14 and '116, wherebythe thermally responsive member remains in the retracted, contacts-openposition. This feature is advantageous in that the movable contacts and112. cannot be closed against the'fixed contacts 76 and 78,respectively, on the faults which cause tripping of the circuit breaker,until the thermally responsive element 1% has cooled for a sufficienttime interval so as to bring arms 1'14 and 116 into position oralignment for engagement by abutment 61.

Further, upon depression of the push button from the retracted to theadvanced or reset position, while the thermal element is still in theexpanded condition with arms 114 and 116 in a condition which does notpermit engagement by abutment 61, the stem 36'will not be latched by themechanical latching means since spring 64 will not be from thedashed-line position shown in FIGS. 2, 5 and 7- to the full-lineposition shown in these figures, the parts are again in the conditionsand positions as shown in FIG. 1 and are ready for resetting of thecircuit breaker, as just described.

Circuit breaker 20 is further capable of being manually actuated for useas an on-off electrical switch. In this regard, with the parts in theadvanced, reset, contactsclosed positions, as shown in dashed lines inFIG. 1 and in full lines in FIG. 6, push button member 32 may be graspedand forcibly pulled outwardly toward retracted position, whereby themanual force applied in conjunction with the upward thrust of spring 120will be suificiently greater than the effective downward thrust ofspring 64 and the wedging action of latching ring against balls 120;thermal element 100 will move upwardly out of engagement with fixedcontacts 76 and 78 under the bias of compression spring 64; the distalends of arms 114 and 116, however, will still be in engagement withabutment 61 of member 58, which will also move to the retracted positionwith movement of the thermally responsive member 100. It should be notedthat the upper surface of portion 140 serves to engage the insulatingwasher 68 to prevent the thermal element from moving downwardly inrelation to member 58 whereby to prevent rarms 114 and 116 from movingto the underside of this member and out of alignment therewith. Surfaceor ledge 170 also may serve to engage the insulating washer 68 andthereby elevate the thermal element upon manual opening of the switch,as described above.

As noted above, the latching forces exerted to retain member 32, stem 36and the parts fixed with respect thereto in the reset position, areindependent of the forces exerted on thermally responsive member ltiil.This is advantageous in that repeated latching and unlatching due tomanual on-oflt' switching of the circuit breaker will not upset thecalibration of the thermally responsive member.

/ Circuit breaker 20 is trip-free in that the thermally responsivemember 100 cannot be retained in a contactsclosed position by forciblyretaining push button 32 in the advanced or reset position upon theoccurrence of a current overload through thermally responsive element100. If button 32 and stem 36 are restrained in the advanced, resetposition by forcibly holding push button 32 in the depressed, advancedposition when the thermally responsive element has warped or deformedsufficiently to disengage the distal ends of arms 114 and 116 fromabutment 61, the thermally responsive member will move to thecontacts-open position under the bias of compression spring 64 (button32 and stem 36 will, of course, remain in the advanced position) andmember 58 will move away from push button 32 from the fullline positionto the broken-line position as shown in FIG. 7, under the bias of spring60.

It will thus be noted that members 32 and 58 will mov to retractedposition under the bias of spring 120 upon release of the externalapplication of the resetting force to the push button. This is becauseno mechanical latching of the stem 36 can take place unless the thermalelement is moved to a contacts-closed position by virtue of theabove-described cooperation of spring 64 with the thermal element andthe latching ring 160.

It will be noted (seeFIG. 4) that when thermally responsive element 100warps upon heating thereof, movable contacts 110 and 112 are urgedrespectively against fixed contacts 76 and 78, thereby causing anincrease in contact pressure. Thus the instant switch affords anincrease in contact pressure with an increase in temperature of thethermal element before tripping at an over-.

from abutment 61 for the release of the thermally responsive member tocontacts-open position.

As arms 114 and 116 move away from each other" upon warping of thethermally responsive element 1% due to heating of the latter when theparts are in the full-line, contacts-closed position shown in FIG. 6, itis likely, or possible at least, that one of these arms will move out ofengagement with abutment 61 slightly before the other. The result willbe that member 58 will tilt about the point of engagement of said otherarm and abutment 61 will move laterally relative to portion 36a of stem36 under the force couple effected by the bias of springs 60 and 64.This tilting and/or lateral movement of member 58 is permitted by'virtueof the clearance as described above between the surface of member 58defining aperture 59 and the outer surface of the stem portion 36a ofstem 36. This tilting and/ or lateralmovement of member 58 permitsdisengagement of said other arm from abutment 61 and movement of thethermally responsive element 1610 to the retracted, contacts-openposition, as shown in fulllines in FIG. 1',

promptly upondisengagement of said one arm from the abutment 61. Lateraland pivotal realignment of memlb is elfected when countersunk or beveledportion 35 moves into engagement with beveled surface 54 of the enlargeddiameter portion 52 of stem 36, under the bias of spring 60, thusforcing member 53 back to laterally and pivot ally aligned relation withthe remaining parts of the switch. Accordingly, abutment 61 which isprovided by member 58, will be realigned for engagement by the distalends of arms 114 and 116 upon the cooling of the thermally responsiveelement 100 from the dashed-line position of FIGS. 2 and 5 to thefull-line position of these FIGURES.

The switch of the instant invention'provides a number of unique andunobvious advantages. One of the advantages of the switch of theinstantinvention is that the structural arrangement of the operatingparts lends itself to the use of compressive resilient biasing meanswhich provides substantial advantages over tension-type springs and thelike. For example, the compression spring 64, which is employed betweenthe thermal latch element and detent means or latching ring 160 providesa number of advantages over that which would be afforded by a tensionspring type arrangement which might involve a number of tension springsand linkages.

By-use. of the compression spring, compactness and miniaturization ofthe switch structure is permitted and only a single spring element isrequired. The compression spring 64 affords a simple and quick assemblyof parts. All that is necessary to assemble the spring in properrelation is to merely dispose it about the latching ring 160, before thethermal element 100 is mounted on the stem 36. i

Further, the compression spring arrangement of the switch of the instantinvention provides a switch with greater vibration stability than thatwhich might be afforded by a tension spring arrangement. The slidablymounted latching ring 160 with its wedge and beveled surfaces, is asimple one-piece construction which permits quick and easy assemblywithout the necessity of close tolerances. The ring is assembled inposition merely by insertion over spring cup 122 before the latter isfixed to the housing by rivet 124. The fact that the mechanical latchingmechanism is enclosed in the well or recess provided by the casing,rather than being an exposed part of the circuit breaker, provides theunique and advantageous result of preventing contact splatter and otherdeleterious debris (such as breakdown of housing material which isgenerallyassociated with high rupture capacity devices) from interferingwith the operation of the mechanical latching mechanism. 7

Further the latching ring 160 provides a positive wedging action througha direct application of compressive force from spring 64, which providesa highly efi icient arrangement. The direct application of compressiveforce and compression spring and slidable latch ring arrangementco-operate to provide latching which is more I afford a force balanceand to increase vibration stability.

Further, the mechanical latching arrangement with its compressivebiasing force-permits the use of a one-piece thermal elementconstruction, and eliminates any necessity for pivoted parts, pigtailarrangements, or other more complex constructions.

It can be seen from the above that the circuit breaker or switch 21)provides a device which is reliable, compact and which is simple inconstruction and economical to manufacture. I

In view of the above, it will be seen that the several objects of theinstant invention are achieved and other unique and unobviousadvantageous results attained.

As many changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings, shall be interpreted as illustrative and not in a limitingsense,

and it is also intended that the appended claims shall I 11 cover allsuch equivalent variations as come within the true spirit and scope ofthe invention.

We claim:

1. An electrical switch comprising a base; contact means on said base;movably mounted means carrying movable contact means for engagement withsaid firstnamed contact means; manually operable means mounted in saidswitch for movement relative to said movably mounted means; thermallyresponsive means for latching said manually operable means and saidmovably mounted means together as a unit for movement in acontactsclosing direction; mechanical latching means for latching saidmanually operable means in a contacts-closed position when the latter islatched to said movably mounted means by said thermally responsivemeans; compressive biasing means compressively urging said mechanicallatching means into latching engagement with said manually operablemeans when the latter is in the contacts-closed position; and saidswitch also including means providing for snap closing of saidfirst-named and movable contact means.

2. The switch as set forth in claim 1 and wherein saidmechanicallatching means is disposed in a recess provided by said base.

3.- An electrical switch comprising contact means; movably rnountedmeans carrying movable contact means for engagement with saidfirst-named contact means; manually operable means mounted in saidswitch for movement relative to said movably mounted means; thermallyresponsive means forlatching said manually operable means and saidmovably mounted means together as a unit for movement in acontacts-closing direction; mechanical latching means for latching saidmanually operable means in a contacts-closed position when the latter islatched to said movably mounted means by said thermally responsivemeans; compressive spring biasing means urging said mechanical latchingmeans into engagement with said manually operable means in thecontactselosed position thereof, said biasing means also urging saidmovably mounted means to a contacts-open position.

4. An electrical switch comprising a base; contact means on said base;movably mounted means carrying movable contact means for engagement withsaid firstnamed contact means; manually operable means mounted in saidswitch for movement relative to said movably mounted means; thermallyresponsive means engageable with abutment means on said manuallyoperable means for latching said manually operable means and saidmovably mounted means together as a unit for movement in acontacts-closing direction; compressive biasing means urging saidmovably mounted means in a contacts-opening direction; mechanicallatching means for latching said manually operable means in acontacts-closed position when the latter is latched to said movablymounted means by said thermally responsive means, said mechanicallatching means comprising detent surfaces on said manually operablemeans; detent means supported on said base for movement into and out ofengagement with said detent surfaces; a latch member movably mountedwith respect to said manually operable means and engageable with saiddetent means for moving the latter into latching engagement with saiddetent surfaces, said biasing means also urging said latch member into,and maintaining the same in, engagement with said detent means in thecontacts-closed position thereof.

5. An electrical switch comprising a base; contact means on said base;movably mounted means carrying movable contact means for engagement withsaid firstnamed contact means; manually operable means mounted on saidswitch for reciprocal movement relative to said movably mounted means;thermally responsive means engageable with abutment means on saidmanually operable means for latching said manually operable means andsaid movably mounted means together as a unit for movement in acontacts-closing direction; said abutment aosavve engageable with andfor latching said manually operable means in a contacts-closed positionwhen the latter is latched to said movably mounted means by saidthermally responsive means; and biasing means compressively urging saidmechanical latching means into engagement with said manually operablemeans .in the contacts-closed position thereof.

6. In combination; a pair of electrical contacts; resetting meanscomprising two members; resilient means compressively biasing said twomembers apart; thermally responsive means operatively connected formovement to open and close said contacts; resilient means compressivelybiasing said thermally responsive means for movement fromcontacts-closed to contacts-open position; one of said two members beingmovable from retracted position to reset position for moving the otherof said two members against a portion of the thermally responsive meansthereby moving the latter to contacts-closed position and compressingsaid second-named resilient biasing means; mechanical latch meansengageablewith said one member for retaining said one member'in resetposition, said second-named biasing means also compressively biasingsaid mechanical latch means into engagement with said one member whenthe latter is moved to the reset position, said thermally responsivemeans being responsive to temperature change for moving said portionthereof out of engagement with said other of said two mem bers therebypermitting movement of the thermally responsive means to contacts-openposition under the bias of said second-named biasing means.

7. In combination; a housing; a pair of electrical contacts in saidhousing; manually operable resetting means; thermally responsive meansoperatively connected for movement to open and close said contacts;compressive resilient means biasing said thermally responsive means formovement from a contacts-closed to a contacts-open position, saidmanually operable resetting means being movable from a retractedposition to a reset position into engagement with said thermallyresponsive means to move the latter to a contacts-closed position andcompress said resilient biasing means; mechanical latch means forretaining said manually operable resetting means in reset position, saidlatch means comprising a detent surcfiace on said manually operableresetting means engageable with ball means mounted for movement into andout of engagement with said detent surface; latch means mounted :formovement relative to said ball means and manually operable resettingmeans, said resilient means also biasing said latch means intoengagement with said ball means to move the latter into and maintain thesame in engagement with said detent surface whereby to retain saidmanually operable reset means in the reset position.

8. The combination as set forth in claim 7 and wherein said mechanicallatch means is disposed in a recess provided by said housing.

9. In combination;-a housing; a pair of electrical contacts in saidhousing; manually operable resetting means; a thermally responsivemember operatively connected for movement to open and close saidcontacts; compressive resilient means biasing said thermally responsivemeans for movement from a contacts-closed to a contacts-open position,said manually operable resetting means being movable from a retractedposition to a reset position into engagement with said thermallyresponsive means to move the latter to a contacts-closed position andcompress said resilient biasing means; mechanical latch means forretaining said manually operable resetting means in reset position, saidlatch means comprising a detent surface on said manually operableresetting means; ball means mounted for movement into and out ofengagement with said detent surface; latch means mounted for movementrelative to said ball means and manually operable reset tingmeans, saidresilient means also biasing said latch means into engagement with saidball means to move the latter into and maintain the same in engagementwith said detent surface whereby to retain said manually operable resetmeans in the reset position; second resilient means biasing saidmanuallyoperable reset means for movement from reset position to retractedposition, said thermally responsive means being responsive totemperature change for moving out of engagement with said manuallyoperable resetting means to thereby permit movement of said thermallyresponsive means to a contacts-open position under the bias of saidfirst-named biasing means.

10. An electrical switch comprising a base; contact means on said base;thermally responsive means operatively connected for movement to openand close said contact means; a first means compressively biasing saidthermally responsive means for movement from a contacts-closed to acontacts-open position; manually operable resetting means comprising twomembers; resilient means compressively biasing said two members apart,one of said two members being movable from retracted to reset positionfor moving the other of said two members into engagement with saidthermally responsive means to move the latter to a contacts-closedposition and compress said first-named biasing means; further resilientmeans compressively biasing said one member from a reset position to aretracted position; mechanical latch means for'reball means to urge thelatter into latching engagement with said latching surface, saidfirst-named resilient means compressively biasing said latch member intoengagement with said ball means when said thermally responsive means ismoved to the contacts-closed position.

11. An electrical switch comprising a base; contact means on said base;movably mounted means carrying movable contact means for engagement withsaid firstnamed contact means; manually operable means mounted in saidswitch for movement relative to said movably mounted means; thermallyresponsive means engageable with abutment means on said manuallyoperable means for latching said manually operable means and saidmovably mounted means together as a unit for movement in acontacts-closing direction; compressive biasing means urging saidmovably mounted means in a contacts-open ing direction; mechanicallatching means for latching said manually operable means in acontacts-closed position when the latter is latched to said movablymounted means by said thermally responsive means, said mechanicallatching means comprising detent surfaces on said manually operablemeans; detent means supported on said base for movement into and out ofengagement with said detent surfaces; a latch member movablymounted withrespect to said manually operable means and engageable with said detentmeans for moving the latter into latching engagement with said detentsurfaces, said biasing means also urging said latch member into, andmaintaining the same in, engagement with said detent means in thecontacts-closed position thereof, said detent means comprising aplurality of balls and said movably mounted latch member being slidablymounted and comprising a latch ring having a wedge surface engageablewith said balls. I

12. In combination; a housing; a pair of electrical contacts in saidhousing; manually operable resetting means; thermallyresponsive meansoperatively connected for ball means mounted for movement into and outof engagement with said detent surface; latch means mounted for movementrelative to said ball means and manually operable resetting means, saidresilient means also compressively biasing said latch means intoengagement with said ball means to move the latter into and maintain thesame in engagement with said detent surface whereby to retain saidmanually operable reset means in the reset position;

said detent surface comprising a peripherally extending groove on saidresetting means; latch means comprising a latching ring slidably mountedwith respect to said ball means and to said manually operable resettingmeans, said latch ring having a wedge surface engageable with said ballmeans for moving the latter into engagement with said peripherallyextending groove under the bias of said resilient biasing means to latchsaid manually operable resetting means in the reset position.

13 In combination; a housing; a pair of electrical contacts in saidhousing; manually operable resetting means; a thermally responsivemember operatively connected formovement to open and close saidcontacts; resilient means compressively biasing said thermallyresponsive means for movement from a contacts-closed to a contactsopenposition, said manually operable resetting means being movable from aretracted position to a reset position into engagement with saidthermally responsive means to move the latter to a contacts-closedposition and compress said resilient biasing means; mechanical latchmeans for retaining said manually operable resetting means in a resetposition, said latch means comprising a detent surface on said manuallyoperable resetting means; ball means mounted for movement in and out ofengagement with said detent surface; latch means mounted for movementrelative to said ball means and manually operable resetting means, saidresilient means also compressively biasing said latch means intoengagement with said ball 7 means to move the latter into and maintainthe same in engagement with said detent surface whereby to retainsaidmanually operable reset means in the reset position; secondresilient means compressively biasing said manually operable reset meansfor movement from reset position to retracted position, said thermallyresponsive means being responsive to temperature change for moving outof engagement with said manually operable resetting means to therebypermit movement of said thermally responsive means to a contacts-openposition under the bias of said first-named biasing means; said detentsurface comprising a peripherally extending groove on said resettingmeans; latch means comprising a latching ringslidably mounted withrespect to said ball means and to said manually operable resettingmeans, said latch ring having a wedge surface engageable with said ballmeans for moving the latter into engagement with said peripherallyextending groove under the bias of said first-named resilient biasingmeans to latch said manually operable resetting means in the resetposition.

14. An electrical switch comprising a base; contactaoaavve of said twomembers being movable from retracted to reset position for moving theother of said two members into engagement with said thermally responsivemeans to move the latter to a contacts-closed position and compress saidfirst-named biasing means; further resilient means compressively biasingsaid one member from a reset position to a retracted position;mechanical latch means for retaining said one member in reset positionwhen said other member is in engagement with said thermally responsivemeans and the latter is in the contacts-closed position, said latchmeans comprising a peripherally extendinglatohing surface on said onemember; ball means mounted on said base for movement into and out ofengagement with said latching surface; a latch member movably mounted onsaid base with respect to said ball means, said latch member having awedge surface engageable with said ball means to urge the latter intolatching engagement with said latching surface, said first-namedresilient means compressively biasing said latch member into engagementwith said ball means when said thermally responsive means is moved tothe contactsclosed position; and said movably mounted latch membercomprising a slidably mounted latching ring.

15. An electrical switch comprising a base; contact means on said base;movably mounted means carrying movable contact means for engagement withsaid firstnamed contact means; manually operable means mounted on saidswitch for reciprocal movement relative to said movably mounted means;thermally responsive means engageable with abutment means on saidmanually operable means for latching said manually operable means andsaid movably mounted means together as a unit for movement in acontacts-closing direction; said abutment means being slidably mountedon said manually operable means; spring means urging said abutment meansfor movement relative to said manually operable means in acontacts-closed direction; mechanical latching means engageable with andfor latching said manually operable means in a contacts-closed positionwhen the iatter is latched to said movably mounted means by saidthermally responsive means; biasing means intermediate saidthermally-responsive means and mechanical latching means compressivelyurging said mechanical latching means into engagement with said manuallyoperable means in the contacts-closed position thereof, and alsocompressively iii-3 urging said thermally responsive means for movementin a contacts-opening direction.

16. The electrical switch as set forth in claim 10 and wherein saidlatch member is mounted for slidable movement with respect to said onemember and said ball means.

17. In combination: a housing; a pair of electrical contacts in saidhousing; manually operable resetting means; thermally responsive meansoperatively connected for movement to open and close said contacts;resilient means compressivel'y biasing said thermally responsive meansfor movement from a contacts-closed to a contacts-open position, saidmanually operable resetting means being movable from a retractedposition to a reset position into engagement with said thermallyresponsive means to move the latter to a contacts-closed position andcompress said resilient biasing means; mechanical latch means forretaining said manually operable resetting means in reset position, saidlatch means comprising a detent surface on said manually operableresetting means engageable with ball means mounted for movement into andout of engagement with said detent surface; latch means mounted formovement relative to said ball means and manually operable resettingmeans, said resilient means also compressively biasing said latch meansinto engagement with said ball means to move the latter into andmaintain the same in engagement with said detent surface whereby toretain said manually operable reset means in the reset position; andsaid latch means being slidably mounted in said casing for movementrelative to said ball means and manually operable resetting means.

References Cited in the file of this patent I UNITED STATES PATENTS2,156,761 Jackson May 2, 1939 2,187,606 Jackson et al Jan. 16, 19402,633,515 Locher Mar. 31, 1953 2,668,886 Ingwersen 'Feb. 9, 19542,798,920 Ingwersen July9, 1957 2,816,192 Ingwersen Dec. 10, 19572,828,385 Malone Mar. 25, 1958 2,831,086 *Ing'wersen et a1 Apr. 15, 19582,833,888 Bessiere May 6, 1958 2,838,635 Ingwersen June 10, 1958.2,839,638 Epstein June 17, 1958

